MCV (Mean Corpuscular Volume) is the average red cell size expressed in femtolitres (fL = 10-15 L). MCV is useful in the differential diagnosis of anemias, which are broken down—based on MCV—into microcytic anemia (below normal MCV), normocytic anemia (normal MCV) and macrocytic anemia (MCV above normal).
Iron deficiency, prolonged or chronic inflammation, chronic bleeding (digestive, uterine), certain hemoglobin production disorders (thalassemia) are the most common causes of microcytic anemias. Normocytic anemias, the most common form of anemias are found in the recuperation phase after an hemorrhagic episode, in hemolytic disorders, in chronic diseases and renal, endocrine (thyroid, pituitary, adrenal) or liver insufficiencies. They can also result from a bone marrow that is unable to produce red blood cells in sufficient amount to meet the body needs (marrow aplasia, myelopathies, myeloproliferative disorders, etc.). Vitamin B12 deficiency (malabsorption, malnutrition, pernicious anemia) and alcoholism are the most common causes of macrocytic anemias. Other causes include thyroid dysfunction and certain bone marrow diseases.